I have the same tower. Some years ago I bought a "half sloper" that was
going for almost nothing on ebay. I think it was the Alpha-Delta version,
but my memory is not very good. It covers 40, 80, 160. Not wanting to get
it too close to my beam on top of the tower (SteppIR), I attached the half
sloper at the top of the second tower section. It works moderately well. I
have about 30 radials of various lengths attached to the tower.
The width of the tower, plus the coax hanging from the tower standoffs,
makes a "thick" antenna and probably helps with bandwith. I can cover the
bottom 50 Khz of 160, and about 300 Khz of 80 meters with an SWR of 3:1 or
less (and I am happy with this). On 40 meters, my sloper is very touchy and
I do not use it much there.
Half slopers are well known to be unpredictable. You may do better or
worse. Even doing worse, I expect it would be better than the little mobile
antenna you are thinking about.
Except for a loading coil for 160, you can easily make your own. The
antenna feed is simply a coax connector on a small metal plate. The plate
is attached to the tower. The center conductor goes to the two sloper wires
(one for 80m and one for 160/40). The wires slope to somewhere near the
ground, at something like a 45 degree angle with the tower. Part of the
tuning is simply moving the wires around (to a greater or lesser angle) and
playing with the lengths a bit.
Bill Ogden - W2WO
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